Automatic grader

ABSTRACT

A system and apparatus for grading and sorting tobacco leaves and the like according to color and brightness are provided. The color of each tobacco leaf is compared photoelectrically with the color of a replaceable background color standard over which each leaf is conveyed. The system can be operated in either a normal mode, i.e., detecting and separating all those leaves darker than the background standard, or a reverse mode, i.e., detecting and separating all those leaves that are lighter than the background standard. A plurality of such systems are set to perform a series of sequential detections and separations, against a selected plurality of background color standards to effect separation of a plurality of tobacco leaves into a preselected number of grades or classifications. The system and apparatus can be embodied in a transducer unit for converting existing tobacco sorting machinery from a manual to an automatic sorting mode of operation. Two color detection of reflected light is used to determine brightness as well as greenness. A separate detector for each color is positioned behind a broad band color filter to sense reflected light from the tobacco leaves and the background standard. Either one or the sum of the resulting signals for each detected color is indicative of the brightness of the leaves while the difference between the signals is indicative of the greenness. A pneumatic reject mechanism is actuated in response to given leaf grade conditions, or a lack thereof, to separate undesired grades of leaves from the plurality of leaves being graded.

United States Patent [1 1 Perkins, II'I [451 Jan, 1, 1974 AUTOMATICGRADER [75] Inventor: Joseph R. Perkins, Ill, Burke, Va.

[73] Assignee: AMF Incorporated, White Plains,

[22] Filed: Aug. 3, 1972 [2!] Appl. N0.: 277,499

Related US. Application Data [63] Continuation of Ser. No. 145,444, May20, 1971.

[52] US. Cl. 209/11l.6, 356/186 Primary Examiner-Richard A. SchacherAtt0rney-George W. Price et al.

[57] ABSTRACT A system and apparatus for grading and sorting tobaccoleaves and the like according to color and brightness are provided. Thecolor of each tobacco leaf is compared photoelectrically with the colorof a replaceable background color standard over which each leaf isconveyed. The system can be operated in either a normal mode. i.e.,detecting and separating all those leaves darker than the backgroundstandard, or a reverse mode, i.e., detecting and separating all thoseleaves that are lighter than the background standard. A plurality ofsuch systems are set to perform a series of sequential detections andseparations, against a se lected plurality of background color standardsto effect separation of a plurality of tobacco leaves into a preselectednumber of grades or classifications. The system and apparatus can beembodied in a transducer unit for converting existing tobacco sortingmachinery from a manual to an automatic sorting mode of opera tion. Twocolor detection of reflected light is used to determine brightness aswell as greenness. A separate detector for each color is positionedbehind a broad band color filter to sense reflected light from thetobacco leaves and the background standard. Either one or the sum of theresulting signals for each detected color is indicative of thebrightness of the leaves while the difference between the signals isindicative of the greenness. A pneumatic reject mechanism is actuated inresponse to given leaf grade conditions, or a lack thereof, to separateundesired grades of leaves from the plurality of leaves being graded.

38 Claims, 5 Drawing Figures PATENTEU JAN 1 I974 SHEET 1 [IF 5 IINVENTOR JOSEPH R. PERM/mm AUTOMATIC GRADER This is a continuation ofapplication Ser. No. 145,444, filed May 20, 1971.

This invention relates to automatic graders and more particularly tosystems and apparatus for automatically grading tobacco leaves and thelike according to color.

In the past and at the present time, it is a normal practice to gradetobacco by manual methods, i.e., by visual inspection of each leaf todetermine given grades of tobacco leaves. Furthermore, should a leaf betoo green for present processing, such as a green sucker, manualinspection is also presently used to remove these leaves from furtherprocessing as undesirable grades.

As a result, arcuate duplication of tobacco grades is very difficult toachieve at the present time. This is due to the difference of opinionwhich exists among manual sorters who must use their own judgment indetermining the grade ofa given tobacco leaf. The eye of the observer isthe standard rather than an actual grade reference.

It is, therefore, an object of the present invention to provide a newand novel automatic grader which can readily duplicate grades of tobaccoleaves and the like through the use of known background color standardsfor any given grade.

It is another object of the present invention to provide a means ofrapidly grading tobacco leaves and the like without the need for manualinspection of each leaf.

It is another object of the present invention to provide a new and novelautomatic grading system and apparatus which operates to grade tobaccoleaves and the like by comparing the color ofa given leaf with abackground color standard over which the given leaf must pass during thesorting and grading process to which it is being subjected.

Still another object of the present invention is to provide a new andnovel automatic grader utilizing a color comparison system which may beembodied in a transducer arrangement for adapting existing manualsorting equipment to fully automatic sorting and grading equipment.

Still another object of the present invention is to provide a new andnovel automatic grader system and apparatus utilizing an uniquecombination of two color detection and resulting detected color signalstrength to provide selective grading of tobacco leaves and the like forboth brightness of color and greenness of leaf.

Yet another object of the invention is to provide a new and novelautomatic tobacco sorting and grading system and apparatus which may beoperated as a series of machines or devices performing a like series ofsorting and selecting functions such that all of the leaves in a givenbatch of tobacco being graded will be separated into desired categories,these categories being determined by various background color standardswhich are interchangeable in each of the said machines and/or devices.

These and other objects of the present invention will become more fullyapparent with reference to the following specification and drawingswhich relate to a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a general schematic of the present invention including thebasic physical details of a preferred optical system for same;

FIG. 2 is a general block diagram of the control circuit of theinvention;

FIG. 3 is a more detailed block diagram of the control circuit of theinvention;

FIG. 4 is a circuit diagram of a single color detector and brightnesscomparator circuit of the present invention including normalizing,updating and reset means; and

FIG. 5 is a circuit diagram ofa two color detector and brightness andgreenness comparator circuits of the present invention includingnormalizing, updating and reset means.

REFLECTIVITY OF TOBACCO LEAVES AND BACKGROUND STANDARDS It has beenascertained that for properly cured tobacco leaves, there is apredictable difference between the reflectivity of orange/light and redlight, the red reflectivity being on the order of 4 8 percent greaterthan the orange, depending upon the type of tobacco and its curingprocess.

This predictable difference will be varied by the greenness of the leafbeing monitored, thereby provding parameters that are determinative ofthe acceptability of a tobacco leaf according to its degree ofgreenness, regardless of its acceptance in a given color grade based onits relative brightness.

Either the red reflectivity or the orange reflectivity of a given leafcan be utilized to effect automatic grading on the basis of relativebrightness of the leaf to a background color standard.

By the use ofa two color system and utilizing the sum of the signalsrepresenting the strength of the red and orange reflected light from theleaf and background standards, improved performance and reliability isef fected. Furthermore, the versatility of this system to detectgreenness of the leaf from the same two reflected light transducers ismade possible.

The optical system A comprises a housing A1 with an elongated telescopetube A2 extending therefrom. An objective lens A3 is mounted in thefront of the telescope tube A2 facing the obverse surface of thebackground reference S and focuses reflected light from the latterthrough an apertured plate A4, defining the field of view of the opticalsystem A.

THE BASIC SYSTEM AND APPARATUS With the foregoing consideration ofreflectivity established, the basic system and apparatus of the presentinvention can best be described by reference to FIG. I, where thegrading means I0 of the present invention is schematically illustrated.

Tobacco leavesT are fed sequentially over a background color standard(platen) S by means of an endless belt conveyor 12 driven by a pulleydrive 12A (or by other suitable conveyor means).

Mounted above the color standard S is a light source comprising a pairof lamps L, a pair of detector means, namely, a red light detector RDand an orange light detector OD.

Over these detector means RD and OD are positioned suitable optics andfilter combinations, namely, a red filter and optics RF and an orangefilter and optics OF, respectively.

The optical system A comprises a housing A1 with an elongated telescopetube A2 extending therefrom. An objective lens A3 is mounted in thefront of the telescope tube A2 facing the obverse surface of thebackground reference S and focuses reflected light from the latterthrough an apertured plate A4, defining the field of view of the opticalsystem A.

The orange filter OF is positioned over the apertured plate A4 such thatonly the orange and red components of light reflected from thebackground reference S and- /or tobacco leaves T will be passed throughthe apertured plate A4.

A field lense A5 is positioned in the telescope tube A2, and directs theorange and red light into the housing A1.

Within the housing Al, the red filter RF is placed transversely of theoptical axis of the telescope tube A2 at an angle of 45 thereto.

The red detector RD (shown as a phototube) is placed behind the redfilter RD to receive only the red component of reflected light throughthe red filter RF.

The obverse surface of the red filter RF serves as a mirror and reflectsthe incoming orange light from the orange filter OF at right angles tothe optical axis of the telescope tube A2 and the orange detector OD(shown as a phototube) is disposed within the housing Al to receive theorange light reflected from the obverse surface of the red filter RF.

The detector means RD and OD are connected via signal leads RDl and OD],respectively, to signal inputs 14A and 14B ofa control circuit 14, thelatter generating a control signal at a control output 16 which signalis conveyed through output lead 16A to the control terminal 18A of apneumatic reject mechanism 18.

The pneumatic reject mechanism 18 includes a solenoid controlled air jet20 which directs a stream of air 20A against the underside of selectedones of the to bacco leaves T, namely, undersired or rejected ones ofthe leaves T to constrain upon the latter a trajectory TR which, whenleaving the background standard S, is predictably different from thetrajectory TA taken by acceptable ones of the leaves T which are of thegrade desired.

The trajectories TA and TR carry the leaves T into a pair of receivingbins or conveyor belts BA and BR, respectively, for acceptable andrejected ones of the leaves T.

As further shown in FIG. 1, the pneumatic reject mechanism has apressure input 18B which is connected to a pneumatic source 22 toprovide the pressurized air for the jet 20.

The light source L is positioned to illuminate the background referenceS and any leaf T thereon and cause reflection of that light back to theoptical system A.

In basic operation, which will be hereinafter more fully described,those leaves T which are within the color limit set by the backgroundreference S, are permitted to fall from the reference S and assume theacceptable trajectory TA into the acceptable grade bin BA.

When a leafT is of a color external of the limit determined by thebackground reference S, this difference is detected by the detectors RDand OD and a resulting control signal is generated in the controlcircuit 14, and thence transmitted through the control output 16,control lead 16A and input terminal 18A to energize the pneumatic rejectmechanism 18 before that particular leaf T leaves the platen shapedbackground reference S.

Accordingly, an upwardly directed stream of air 20A is emitted from thejet 20 and lifts the rejected (undesirable) leaf T to constrain it intothe reject trajectory TR and into the reject bin BR, effecting aselective grading of the tobacco leaves T.

As will be hereinafter more fully described, the duration of theairstream 20A is timed such that it will not interfere with thetrajectory of the next successive leaf T unless the latter is not withinthe color limits of the background reference S,

THE FUNCTION OF THE BACKGROUND REFERENCE S AND THE VARIOUS GRADING MODESOF THE INVENTION The tobacco grading means 10 operates by comparing thecolor of the tobacco leaves T with a selected replaceable backgroundreference S. The color of the background reference S acts as a dividerbetween the color of the tobacco leaves T that are to be kept and thecolor of the tobacco leaves T that are to be rejected.

There are two modes of grading which are selectively initiated in theapparatus and means of the present invention.

The first mode is the normal grading mode. In the normal grading mode,all leaves that are lighter than the background reference S will beretained in the acceptable bin BA. By the same token, all those leaveswhich are darker than the background will be constrained into the rejecttrajectory TR and captured in the reject bin BR by the tobacco grader10. It should be clearly understood that the color of the backgroundreference S is not the color of the desired grade of tobacco leaf T, butis the color of the darkest leafT that is to be kept, i.e., the darkestleafT that is to be captured in the acceptable bin BA. Therefore, thecolor of the background reference S corresponding to a particular gradeof tobacco leaf T will not be the same color as an average leafT in thatgrade, but will be somewhat darker than average.

By way of specific example of the normal grading mode, let us firstassume that the background reference S is red-orange in color.Consequently, all yellow and orange leaves T will be permitted to followthe acceptable trajectory TA into the acceptable bin BA because they arelighter than the background reference S. Likewise, all red, brown, andblack leaves will be rejected because they are darker than thebackground reference S.

The alternate mode of grading is known as reverse grading and isperformed by setting suitable controls on the tobacco grader 10 to causerejection, via the trajectory TR, of all leaves T that are lighter thanthe color of the background reference S.

By way of specific example, if the background reference S is coloredyellow-orange, the reverse grading mode of operation will cause allyellow leaves to be constrained to the reject trajectory TR and willpermit all orange, red, brown and black leaves to follow the acceptabletrajectory TA into the acceptable bin BA. Therefore, in the reversegrading mode, the color of the background reference S corresponding to acertain desired grade of tobacco leaf T will be somewhat lighter thanthe average leaf for that desired grade.

If a plurality of tobacco graders 10 of the present invention are placedin series, a plurality of grades can be effectively isolated from agiven bath of tobacco leaves T.

By way of specific example, if two tobacco graders are put in series andthe first of these graders is set for the reverse grading mode with ayellow-orange background and the second of these tobacco graders 10 isset for a reverse grading mode with an orange-red background then allyellow tobacco would be constrained into the reject bin BR of the firstgrader 10, all orange tobacco would appear in the reject bin BR of thesecond tobacco grader l0, and the red, brown, and black tobacco leaves Twould be passed through the first and second tobacco graders 10 toultimately end up in an acceptable bin BA at the second grader.

Furthermore, should it be desired to further separate the red leavesfrom the brown and black leaves, another grader 10 could be set up downstream from the first two in a reverse grading mode wherein thebackground reference is colored red-brown and thereby, all of thelighter leaves, namely, the red leaves T would be constrained into areject trajectory TR while the browns and blacks would be passed toacceptance bin BA at the third grader.

A further function of the tobacco grader 10 of the present invention isfor the separation of the tobacco leaves which are too green for furtherprocessing. This will be hereinafter referred to as the separation oftobacco leaves T according to greenness.

As with the separation on the basis of brighness of the color of theleaves T, the greenness of background reference S determines thedivision of the accepted and rejected tobacco leaves T. in the normalgrading mode, these leaves T that are greener than the backgroundreference S will be rejected and those leaves T that are not as green asthe background reference S will be accepted.

By way of specific example, if the background reference S is agreenish-red-orange and all green leaves are bieng rejected, than agreen sucker or a green-yellow leaf would be rejected and all yellow,orange, red, and brown leaves would be accepted by the grader 10.

in the same manner that the background reference S must be darker thanthe desired grade when operating the tobacco grader T0 the normalgrading mode for brightness, the background reference S, in grading forgreenness must be somewhat greener than the desired grade. lt must notbe as green, however, as the leaves T that must be rejected.

Intermingling of the brightness and greenness constraints in the tobaccograder 10 is effective, selectively, to provide various controlfunctions on such tobacco leaves T as greensuckers and sweat greens.These combined functions will be hereinafter more fully described withreference to the more detailed embodiments to follow.

THE REFLECTED COLORS DETECTED AND THEIR CORRELATION WlTH BRIGHTNESS ANDGREENESS SIGNALS The tobacco grader It) employs two broad band lightfilters with related optics, namely, the red filter RF, the orangefilter and optics A. The red filter is centered at approximately 65 5nanometers (nm). The orange is centered at abolit Gil (Yum. Therespective red and orange light detectors RD and OD provide outputsrepresentative of the strengths of the reflected orange and red lightcomponents from the background reference S and a leaf T on thatbackground and such output signals are either added to obtain abrightness signal or subtracted to obtain a greenness signal.

The brightness signal can be obtained from either one of the red andorange detectors RD and OD. However, by adding the two signals from thesaid detectors,

the signal to noise ratio of the tobacco apparatus 10 is improved. Themagnitude of the brightness signal obtained is a measure of the color ofthe leaves, because red leaves are darker than orange leaves which inturn are darker than yellow leaves. Therefore, the red and yellow lightcomponents and the intermix of same are the critical colors of reflectedlight to determine the brightness of a given tobacco leaf T relative tothe background reference S.

The greenness detection function makes use of some of the properties ofgreen light as opposed to red and yellow light. Green light is producedby reflection of white light from a surface if the blue and red ends ofthe spectrum are absorbed by the surface leaving the green middleportion of the spectrum. Yellow and red light, on the other hand, aretypically produced when the blue end of the spectrum is absorbed and themiddle portion is partially absorbed leaving the red end of thespectrum. in both cases, the blue end of the spectrum is absorbed.Therefore, to tell green light from red or yellow light, only two lightfilters and detectors are required, namely, one in the middle of thespectrum (orange, for example) and one in the red end of the spectrum.If the light from the middle of the spectrum is stronger than the lightfrom the red end, then the reflecting surface is green; if the lightfrom the red end is stronger than the light from the middle of thespectrum, the reflecting surface could by yellow, orange, red or brown.

In the case of the preferred embodiment of tobacco grader 10, an orangefilter is used rather than one nearer the middle of the spectrum such asa green or yellow filter. This is due to the fact that the orange filterworks just as well for the greenness determination and has the advantageof providing a stronger signal since the reflectivity of green tobaccoleaves is generally greatest in the orange part of the spectrum.

in the case of tobacco leaves it is rare to find a truly green leaf suchas on a living plant. More typically, the leaves are greenish, i.e.,greenish yellow, greenish orange, etc. In these cases, the orange signalis not necessarily stronger than the red signal as would be the case fora truly green leaf. The distinctive factor is that the differencebetween the reflected red and reflected orange signals is not as greatfor a greenish leaf as it is for a normal acceptable leaf.

For a normal flue-cured tobacco leaf, the difference between its redreflectivity and its orange reflectivity is approximately 8 percent.That is to say, if a yellow fluecured leaf reflects 50 percent of theorange light (600 nm) it will reflect 58 percent of the red light (670nm). Ifa red flue-cured leaf reflects 20 percent of the orange light, itwill reflect 28 percent of the red light. On the other hand, a yellowleaf which reflects 50 percent of the orange but reflects only 52percent of the red light would appear to be greenish. Likewise, a redleaf which reflects 20 percent of the orange light but only 23 percentof the red light will also appear to be green.

Since the determination of greenness and the degree of greenness isrelative to the strengths of the red and orange brightness signals, itis best to pick a background for flue-cured tobacco that is about 4percent more reflective in the red than in the orange. For other typesof tobacco, a different factor may be required although the figure of 4percent appears to work as well with air cured Burley tobacco as withflue-cured tobacco leaves.

As an additional benefit, white objects which may be intermingled withthe tobacco leaves being graded will appear to be green since the whiteobjects will reflect red and orange light in equal strengths. It istheoretically possible, therefore, to pick up a piece of string or othersmall impurity with the tobacco grader l and reject the same ifsufficient sensitivity is provided in the control circuit 14.

THE CONTROL ClRCUlT 14 Referring now to FIG. 2, the general details ofthe control circuit 14, first described with reference to FIG. 1 will befurther defined.

The control circuit 14 is shown as including the red and orange lightdetectors RD and OD respectively, which are connected through thecontrol circuit input terminals 14A and 148 to red light and orangelight detector networks RDN and ODN, respectively.

The red and orange light detector networks RDN and ODN have outputterminals 30 and 32, respectively, which are mutually connected to theinput terminal pairs of an adder circuit 34 and a subtractor circuit 36.The adder circuit has input terminals 34A and 348 connected,respectively, to the orange output 32 and the red output 30 of the saiddetector networks ODN and RDN. The subtractor circuit 36 has inputterminals 36A and 36B connected, respectively, to the orange output 32and the red output 30 of the said detector networks ODN and RDN.

The adder output terminal 34C is directly connected to the inputterminal 38A of a bright or dark detector circuit 38, the latter havingan output terminal 388. The output terminal 36C of the subtractorcircuit 36 is directly connected to an input terminal 40A of a green oryellow detector circuit 40, the latter having an 0utput terminal 408.The outputs 38B and 40B of the bright or dark detector circuit 38 andthe green or yellow detector circuit 40, respectively are connected tothe input terminals 42A and 42B, repesectively, of a backgroundreference color storage circuit 42 and the respective input terminals44A and 44B of a logic network 44.

The logic network 44 includes first and second output terminals 44C and44D, respectively, the first output terminal 44C comprising a backgroundpresence signal output which is directly connected to a thrid inputterminal 42C of the background reference color storage 42. Thebackground reference color storage circuit 42 further includes first andsecond output terminals 42D and 425, respectively, which are directlyconnected to second input terminals RDNl and ODNl, respectively, of thered and orange light detector networks RDN and ODN.

The second output terminal 44D which comprises a color output from thelogic circuits 44 is directly connected to the input terminal 46A or acolor rejection selector circuit 46, the latter having an outputterminal 46D directly connected to the input terminal 48A of an airsolenoid driver and delay circuit 48. The air solenoid driver and delaycircuit 48 has an output terminal 48B which is coincident with thecontrol output terminal 16 of the control circuit 14. Therefore, theoutput of the air solenoid driver and adjustable delay circuit 48 drivesthe pneumatic reject mechanism 18 by directing a signal to the inputterminal 18A thereof and selectively effecting a blast of air 20A fromthe nozzle 20.

The various functions of the foregoing circuit means are as follows:

1. The orange light detector network ODN produces a signalrepresentative of the amount of orange light reflected from a tobaccoleaf as compaired to the particular background upon which the leaf isbeing examined.

2. The red light detector RDN provides a signal at its output 30 whichis representative of the amount of red light reflected from a tobaccoleaf, compared to the background color upon which the leaf is beingexamined.

3. The adder circuit 34 received at its input terminals 34A and 34B theoutputs of the red and orange light detector networks RDN and ODN,respectively, and adds these signals to obtain a measure of brightnesssignal at the output terminal 34C thereof.

4. The subtractor circuit 36 receives at its input terminals 36A and36B, respectively, the output signals from the output terminals 32 and30 of the orange and red light detector networks ODN and RDN, andgenerates a difference signal between the inputs, which differencesignal appears at the output terminal 36C of the subtractor 36.Therefore, the signal at the output terminal 36C of the subtractorcircuit 36 is a measure of the greenness of a tobacco leaf as comparedto the color of the given background. In the particular mode ofoperation shown, the orange signal is subtracted from the red signalsuch that when a negative output appears on the output terminal 36C ofthe subtractor 36, the leaf being examined by the orange and reddetectors OD and RD is green. Conversely, when the difference betweenthe orange and red signal is positive, the tobacco leaf is yellow,orange, red or brown.

5. The bright or dark detector circuit 38 is designed to emit at itsoutput terminal 38B digital signals to indi cate if the leaf beingexamined is brighter than the background reference, darker than thebackground reference or if there is no leaf present upon the backgroundreference.

6. The green or yellow detector circuit 40 is designed to emit at itsoutput terminal 40B digital signals to indicate if the leaf beingexamined is not greener than the background reference, greener than thebackground reference, or if no leaf is present upon the backgroundreference.

7. The logic circuit 44 functionally determines whether there is a leafpresent upon the background reference or not. The background presencesignal appears on the first output terminal 44C of the logic network 44and is presented as a digital 1 if only the background is in view and asa digital 0 if a leaf is present on the background reference within thefield of view of the red and orange detectors RD and OD, respectively.The logic network 44 is also designed to store for one clock cycle thebright/dark and green/not green data from the detectors 38 and 40. Boththe leaf presence signal on the first output terminal 44C and the degreeof brightness and greenness signal on the second output terminal 44D ofthe logic network 44 can be ascertained by the relationship between theoutputs of the birght or dark detector circuits 38 and the green oryellow detector circuits 40 as applied to the inputs 44A and 44B of thelogic network M.

8. The color rejection selector network 46 may be pre-programmed toselect any of four combinations of bright and green leaves forrejection. These categories are: (1) dark -lgreen; (2) light green; (3)dark not green; and (4) light not green; relative to the color of thebackground reference S. This network requires signals from both thegreenness and brightness detectors via the signal terminal 44D of thelogic network 44 and its own input terminal 46A. The signal on thesecond output terminal MD of the logic network 44 as ap plied to theinput terminal 46A of the color rejection selector 46 may comprise logicsignals which correspond to one of the four combinations to which thecolor rejection selector network 46 will respond. Therefore, the colorrejection selector network 46 is programmed such that upon coincidenceof a logic signal at the input terminal 46A with a preselected color tobe rejected, an output control signal will appear on the output terminal488 of the color rejection selector network 46 which will be transmitteddirectly to the input terminal 48A of the air solenoid and delay network48.

9. The air solenoid driver and delay network 48 is programmed consistentwith the programming of the color rejection selector network 46 and,therefore, is designed to select any of the four combinations of brightgreen" leaves for rejection. This network includes a delay means withmemory (not shown) to compensate for the time delay required for themovement ofa leaf across the background reference into the area in whichair from the nozzle 20 in the pneumatic reject mechanism Hi can engagethe leaf. Upon the receipt of a reject signal at the input terminal 48Aof this circuit, a control signal is generated at its output terminal48B and transmitted through the output terminal 16 of the controlcircuit 14 to the input terminal 18A of the pneumatic reject mechanism18, whereby the pneumatic source 22 is connected through the pneumaticterminal 108 to the nozzle 20 and a blast of air 20A is impinged uponthe leaf to be rejected to constrain that leaf in the reject trajectoryTR. The blast of air is of a duration that corresponds with the size ofthe leaf T.

ID. The background reference color storage network 42 is designed tostore the amount of signal provided by the background reference S whenno leaf is present. Each time a leaf is absent from the backgroundreference S a reading is taken through the orange and red detector meansOD and RD, respectively, and the color signal strength in storage in thenetwork 42 is updated. A timer 42Q2 is also provided in this network toreset the memory therein completely at the time of initial turn-on orany other similar event regarding the control circuits M. The red signalstrength detected from the background reference S stored in thebackground reference color storage network 42 is transmitted through itsfirst output terminal 42D to the second input terminal RDNl of the redlight detector network RDN and thereby subtracted in that network fromthe signal produced in the red light detector RD. Therefore, when noleaf is present and only the background is in view of the detector RD, anull output is obtained from the red detector network RDN. Bytransmitting the orange signal strength from the background reference Sthrough the second output terminal 42E of the background reference colorstorage network 42 to the second input terminal ODN] of the orange lightdetector network ODN and subtracting this signal from the reflectedorange signal detected by the orange detector OD, the orange detectornetwork ODN will also exhibit a null output when no leaf is present uponthe background reference S. The updating function of the backgroundreference color storage 42 is performed to maintain an accurate and truenull signal when no leaves are present upon the background reference Sthroughout a run of a batch of tobacco leaves through the tobacco grader10.

Referring to FIG. 3, a more detailed block diagram of the controlcircuit 14 will now be described, with like elements to H6. 2 bearinglike numerals.

The red and orange detector networks RDN and ODN are shown as includinghilgh impedance followers RDNA and ODNA, respectively. The second inputterminals RDNl and ODNl of the red and orange detector networks RDN and()DN, respectively, are shown as directly connected at the red andorange detectors RD and OD, respectively, such that the reflected lightfrom the background reference S can be nullified at the detectors, priorto amplification of the response of the said detectors to the reflectedlight.

The adder network 34 of Fit]. 2 is combined in a signal balancingnetwork 340 having input terminals 34QA 3408 connected to the outputs 32and 30, respectively, of the high impedance followers ODNA and RDNA tocombine the outputs of the latter to produce a red orange signal.

The red orange signal is amplified (by a factor of 1000, for example) ina conventional comparator circuit 3801, which produces either a high orlow level output voltage at an intermediate terminal 38A] in the brightor dark detector circuit 38, from whence a high and low voltage detectornetwork 3802 generates appropriate digital output states on a pair ofoutput terminals 3881 and 3882, which, together, are equivalent to thegeneral terminal designation 3:88 in the embodiment of FlG. 2.

The orange-red signal is calculated and amplified (by a factor of 2,000,for example) in a greenness comparator circuit 36 (subtractor' circuit36 of FIG. 2) and the amplified difference signal voltage produced atthe intermediate output terminal 36C, from whence it is directed intothe green and yellow detector network 40, the latter comprising a secondhigh and low voltage detector network 40C) for generating appropriatedigital output states on a pair of output terminals 4081i and 40132which, together, are equivalent to the general terminal designation 40Bof the embodiment of FIG. 2.

Thus, on the terminals 3881, .3882, 4081 and 4082 of the bright" andgreen detector networks 38 and 40 are digital signals representative ofthe color of tobacco leaves T, relative to the background reference S aswell as an indication of the presence or absence of such leaves over theobverse face of the background reference S.

All of these terminals are interconnected with the logic circuit 44 suchthat all of the comparative information is fed from the terminals 38131,38132, 4081 and 4082 to the logic circuit input terminals 44Al, 44A2,44B] and 44B2, respectively.

The logic circuit 44 has two logic blocks connected with these logicinput terminals, namely, a leaf detection circuit 4401 and a color datastorage circuit 4402.

The intermediate output terminals 38A1 and 36C of the brightness andgreenness comparators 3801 and 36, respectively, are cross connected tothe data input terminal pair 4201A of a reference gate 4201 in thebackground reference color storage network 42.

The update reference gate has a third data input terminal 4201B which isdirectly connected to the leaf presence output terminal 44C of the leafpresence logic block 4401 of the logic circuit 44.

Also connected to the leaf presence output changed a leaf presence timerinput terminal 4202A of a leaf presence timer network 4202. The timernetwork 4202 has a clock input terminal 4202B connected to a commonsystem clock generator CG and an enabling output 4202C directlyconnected to a fourth input terminal 4201C of the reset reference gate4202. As will be hereinafter more fully described, the clocked leafpresence timer 4202 is responsive for storing the color of thebackground in the background reference storage 4203 when the unit isturned on or the background platen S is changed and insures that thiscondition endures while leaves T are being graded.

The outputs 4201D of the reference gate 4201 are connected to respectiveinputs 4203A of a background color reference store 4203, the output42038 of the latter being connected through a greenness set module 4204controlled from the color selector means 46. Subject to the imposedcolor constraint from the color selector means 46, the balance betweenthe response of the red and orange detectors RD and OD is modified overand above the constraints imposed thereon by the information in thebackground color reference store 4203, to thereby superimpose a desiredgreenness response on the red and orange response characteristics of thesaid detectors, i.e., a degree of greenness sensitivity adjustment.

The color logic storage block 4402 of the logic circuit 44 has itsoutput 44D connected to the input terminal 46A of a color logic decodingcircuit 4601 of the color selector network 46. The storage providesconti nuity between the clock pulses that are used to gate" the systemin time with the 120HZ A-C ripple in the light output of the lamps L.

The color logic decoding circuit 4601 has a constraining nput 4601Aconnected directly to the output 4602A of a manual color selector switchboard 4602, the latter being a preset device for effecting apredetermined output function of the logic decoding circuit 4601 inresponse to the color logic stored in the color logic storage block4402. This output function appears at the output terminal 468 of thecolor selector network 46, from which it passes through the inputterminal 48A into a shift register and gate 4801, the latter comprisinga delay line in the air solenoid driver and a means of requiring thatthe reject signal be present for a period of time to effect rejection,hence eliminating response to false and spurious signals.

The output of the shift register and gate 4801 is fed to the input of asolenoid pulse generator 4802, which is also constrained by a directconnection 4802A to the clock generator CG to produce an on-off pulse ofthe length equal to the length of the leaf T plus enough time tocompensate for the delay in the air lines of the reject mechanism 18.

The output of the solenoid pulse generator 4802 is connected to energizea solenoid driver circuit 4803 which generates the on and off full cyclepulses for the solenoid valve control terminal 18A in the pneumaticreject mechanism 18, to energize the latter to emit a blast of air 20Afrom the nozzle 20 thereof over a period of time sufficient to constraina rejected leaf T in the reject trajectory TR as previously describedwith reference to FIG. 1.

To complete the synchronization of the control logic 14 with the IZOI-IZripple from the lamps L, the logic blocks 4401 and 4402 of the logicnetwork 44 are both constrained by direct input connections 4401C and4402C to the clock generator CG.

The interconnection of the greenness set network 4204 with the colorselector network 46 is schematically illustrated by the dotted lineinterconnection 46M extending from the said greenness set network to thesaid switchboard 4602 of the selector network 46. This interconnectionmay be of the manual type or the electrical type, within the purview ofthose of ordinary skill in the art, to modify the responsecharacteristic of the red and orange light detectors RD and OD.

INTERACTION OF LIGHT DETECTOR, BACKGROUND REFERENCE STORAGE AND LEAFSENSING LOGIC SIGNAL TO PRODUCE BRIGHT AND/OR DARK OUTPUT SIGNALSReferring now to FIG. 4, a simplified version of a brightness detectorcircuit will be described which includes the following equivalentelements from the embodiment of FIG. 3:

1. One of the red and orange light detectors RD and OD;

2. One of the high impedance amplifiers ODNA an RDNA;

3. Brightness comparator circuit 3801;

4. High and low voltage detector network 3802;

5. Background reference storage and delay circuit 42 exclusive of thefront panel greenness selector 4204.

These are the essential analog logic elements needed to produce dark andbright digital logic outputs to ultimately control the pneumatic rejectmechanism 18 of the previous embodiments. These logic outputs are thosethat appear on output terminals 38B1 and 3882 of the embodiment of FIG.3.

The circuit will now be described with reference to the orange lightdetector OD and its accompanying circuitry as representative of a moresophisticated circuit in which two light inputs, namely, that of theorange detector OD and that of the red detector RD are utilized.

The orange detector OD is illustrated as comprising a photo-tube havinga light receiving cathode CDC and an output anode ODA, the latter beingconnected through a load resistance R1 to the input terminal ODNl of theorange detector OD. As previously described with reference to FIG. 2 and3, the input terminal ODNI of the orange detector OD is directlyconnected to the input terminal 42E of the background reference colorstorage circuit 4203.

The background reference storage circuit 4203 is shown as comprisingfirst and second oppositely polarized capacitors C1 and C2 of equalvalue, connected in series from the output terminal 42E to ground. Thecathode ODC of the orange detector OD is connected to a negative voltagebias terminal ODZ, which for purposes of illustration is indicated ascarrying a negative 20 volts.

The anode ODA of the orange detector OD is directly connected to theinput gate terminal of the detector amplifier circuit ODNA which isshown as comprising a field effect transitor connected in voltagefollower configuration, one of its load terminals 102 being connected toa positive 15 volt bias and the other of its load terminals comprisingthe output terminal 32 of the amplifier ODNA and being connected througha resistance R2 to the negative voltage bias terminal B2.

One alternate form of this circuit is to use a semiconductor diode inplace of the photo-tube for light detection. Another alternative is toreplace the phototube OD and the field effect transistor follower ODNAwith a photo-sensitive field effect transistor. In the latter case thelogic outputs must be reversed.

The brightness comparator 3801 is shown as a differential operationalamplifier having a positive bias ter minal 1114, connected to a 15 voltbias source, and a negative bias terminal 1116 connected to a -l voltbias source. As previously described, the output of the brightnesscomparator 3801 is designated as output terminal 381 11. The inputterminals 38A of the operational amplifier 38(11 comprise a pair ofinput terminals 38AA and 38AB. The input terminal 38AA is directlyconnected to the output terminal 32 of the orange detector inputamplifier ODNA and the input terminal NAB is connected to the sameground as the capacitors C1 and C2.

The gating portion of the background reference storage circuit d2,namely, 1201-3 is shown as comprising a field effect transistor having agate terminal 108 connected to the leaf detection logic output 44C and apair of load terminals 110 and 112, the terminal 110 being directlyconnected to the output terminal 38A1 of the brightness comparatorcircuit 3801 and the load terminal 112 being connected through a loadresistance R3 to the output terminal 42E of the background referencestorage 4204.

The bright and dark detector circuit 3802 is shown as comprising a firsttransistor 02A having base emitter and collector terminals 114, 116 and118, respectively, and a second transistor O28, of opposite polarityfrom the first, having base, emitter and collector terminals 120, 122and 1121, respectively. The base terminals 114 and 120 are commonlyconnected to an input terminal 126 which in turn is connected through aninput resistance R4 to the output terminal 38A1 of the brightnesscomparator circuit 3801. The collector terminal 118 of the firsttransistor O2A is connected through a biasing resistance R5 to apositive volt bias source, while the emitter terminal 1 16 thereof isconnected to a positive 8 volt reference source. These voltages areexemplary and are not intended as specific limitations. The collectorterminal 124- of the second transistor (22B is connected through a biasresistance R6 to a negative 15 volt bias source while the emitterterminal 122 is connected to it by negative voltage reference sourcewhich is indicated as 8 volts by way of example.

The collector terminal 118 of the first transistor 02A corresponds tothe first output terminal 38B1 (the bright" terminal) of the bright anddark detector network 3802. The collector terminal 124 of the secondtransistor 02B corresponds to the second output terminal 38132 (thedark" terminal) of the bright and dark detector network 38(22.

in operation, light reflected from the tobacco leaves T and backgroundreference S (not shown in FIG. 4) strikes the cathode ODC of the orangedetector OD causing electrons to be knocked off the said cathode by thephoto-electric effect. The electrons are drawn to the anode ODA by theapproximately 20 volt bias across the detector photo-tube OD. Themovement of these electrons causes the photo-tube OD to act like a veryhigh impedance current source.

Since the photo-tube OD acts like a current source, the bestsignal-to-noise ratio is obtained when the load resistor R1 thereof isas high as practical. The high impedance of the load resistor R1requires the use of a high impedance detector amplifier ODNA, which hasalready been described as a high impedance junction field effecttransistor connected in a voltage follower configuration to drive theinput 38AA of the brightness comparator network 38Q1, the latter beingshown as a differential operational amplifier.

Increased light striking the cathode ODC causes current to flow into thephoto-tube OD through the load resistor R1 from the background referencestorage capacitors C1, C2 via the terminals 4213 and ODNl. Therefore,the voltage appearing via the output terminals 32 of the amplifier ODNAand at the first input terminal 38AA (negative input) of the brightnesscompar ator network 3801 will be the same as the voltage across thebackground reference storage capacitors C1, C2 less than the voltagedrop in the load resistor R1 caused by the photo-current and the smallbias re quired for the gate terminal of the field effect transistor inthe detector amplifier ODNA. The differential action of the brightnessdetection network 38Q1 amplifies the difference between the light inputsignal detected by the orange detector OD and the ground referenceapplied to the positive input terminal 38AB. A very high gain on theorder of about 2,000 is employed by way of example.

With the exemplary bias and reference voltages as shown, for example, apositive swing of 8.5 volts at the output 38A1 of the brightnesscomparator 38Q1 will indicate that increased light is hitting thecathode ODC of the orange detector OD and will cause the firsttransistor QZA in the bright and dark detector network 38(22 to turn on.This will cause a commensurate voltage change at the collector 118 andoutput terminal 3831, thus producing a bright output signal on theoutput terminal 311181. On the other hand, a negative swing at theoutput 38A1 of the brightness comparator network 3801 on the order of8.5 volts, will indicate that less light is being reflected onto thecathode ODC of the orange detector OD and will cause the secondtransistor Q28 in the bright and dark detector 38(12 to turn on, therebygenerating a dark signal via the collector 124 on the second outputterminal 3852 of the bright and dark detector 38Q2.

For purposes of grading tobacco leaves, it is desirable to have theoutput 28/11 of the brightness comparator 38Q1 stationary at a nearground potential when the background reference 5 is being viewed so thatneither a bright]nor a dark signal is produced in the bright and darkdetector circuit 3802. This is accomplished by use of a conventionalnegative feedback loop via the feedback resistence R3 and the loadterminals and 112 of the field effect transistor comprising the gatingcircuits 4201-3 of the background. reference storage circuitry 42. Thegate 42Q1-3 will be turned off by the signal from the leaf sensing logicoutput 44C when a leaf is being viewed.

During this viewing of the leaf, the appearance of the backgroundreference S is effectively stored in the storage capacitors C1, C2(background reference storage 4203) since the effect of the negativefeedback through the gates 4201-3 is such as to place a voltage on thecapacitor C1, C2, sufficient to counter-balance the voltage drop in theload resister Rll of the orange detector OD which is produced by orangelight reflected from the backgreound S striking the cathode ODC.

The feedback resister R3 prevents the voltage on the storage capacitorCll, C2 from changing too rapidly, and the input resistence R4 betweenthe output terminal 38A] and the common input terminal 126 of the brightand dark detector 3802 prevents the first and second transistors 02A and02B of the latter from shorting out the output signal of the brightnesscomparator amplifier 3801. As previously described, the backgroundreference storage circuit 4203 is made in a non-polarized configurationby placing two polarized capacitors Cl and C2 back-to-back.

The feedback gating transistor 4201-3 performs two functions. The firstfunction, already described, is to turn off the negative feedback loopwhen a leaf is being viewed so that false data is not stored in thebackground reference storage circuits 4203, thereby precludingovershooting. The second function is to gate the negative feedback loopso that alternating current can be used on the light sources thatilluminate the viewing area of the background reference S. Since thelight output of lamps used on alternating current is about one-eighth ofthe alternating current frequency in nature, considerable alternatingcurrent will occur in the output of the differential brightnesscomparator amplifier output 3801. By gating the negative feedback intime with the alternating current from the supply mains, essentially thesame results as using direct current in the light sources is obtained.

The logic circuits which follow the AC and DC amplifier must besimilarly gated, of course, and this is accomplished by conventionalmethods.

THE TWO-COLOR CIRCUIT Referring to FIG. 5, wherein like numerals toFIGS. 1 4 denote like elements, there is shown a more specificrepresentation of the details and interconnections of the detectornetwork DN, balance adjustment network 340, brightness detector 38,greenness detector 40, update-reset gates 4201-02, background referencestore 4204 and greenness set 4205.

The red and orange balance adjustment network 340 is shown as includinga summingjunction SJ at the negative input terminal 38A of thebrightness comparator 3801, the said summing junction SJ being connectedthrough a first summing resistence RS1 to the output terminal 32(designated as 32 34aA in common with the balance input 340A) of theorange detector amplifier ODNA and through a second summing resistenceRS2 to the output terminal 30 (designated as 30 340B in common with thebalance input 3408) the red detector amplifier RDNA.

The balance network 340 is completed by connecting the output 32 340A ofthe orange detector amplifier ODNA to ground through a balanceresistence RB having a variable tap RBI thereon connected with thepositive input terminal 363 of the greenness comparator 36; and byconnecting the output 30 340B of the red detector amplifier RDNA throughan input resistence RS3 to the negative input terminal 36A of thegreennesscomparator 36. V g I The feedback loop of the brightnesscomparator 3801 includes a first stabilizing resistence RS1 connectedfrom the output 38A1 thereof to its negative input 38A; while thefeedback loop of the greenness comparator includes a second stabilizingresistence SR2 connected from the output 36C thereof to its negativeinput 36A.

The greenness set 4204 is shown as including auxiliary load resistenceR4 in series between the output terminals 42033 of the backgroundreference store 4204 (in the configuration described in reference toFIG. 4) and the load resistence R1 of the orange and red detectors ODand RD, respectively.

Each such auxiliary load resistence R4 is shunted by a field effecttransistor 03 which is selectively gated to shunt its associatedauxiliary load resistence R4 out of the circuit to vary the sensitivityof response of the red and/or orange detectors RD and OD to the lightreflected from the background reference S and/or tobacco leaves T. Thishas been generally described in reference to FIG. 3.

The speed of establishing the proper reference voltage in the backgroundreference store 4203 (capacitors C1 and C2) for each of the red andorange detectors RD and OD, can be varied by controlling the duration ofthe enabling signal placed upon the gate terminal of the transistors 03in the reference gates 4204.

The duration of the enabling signal is controlled by the leaf presencetimer 4202 (FIG. 3), which causes a rapid reset of the reference store4203 in the event of an abnormally long duration (6 seconds, forexample) between the successive sightings of the background reference Sby the detectors RD and OD.

This condition denotes such occurrences as a memory loss, a leafT stuckon the obverse surface of the reference S or a change from one referenceto another, and suitable alarms and/or surface clearing devices arecontemplated and can be provided to indicate correct those conditionswhich are adverse to the proper operation of the tobacco grader 10.

As indicated in FIG. 5, by way of example, the output voltages of thebrightness and greenness comparators can be normalized to zero when thedetectors OD and RD are viewing the background reference S in theabsence ofleaves T thereon. 7

When the output voltages swing plus or minus 8 volts or greater thesignals represent the intermediate output parameters which define thelogical states LIGHT NOT GREEN LIGl-IT" GREEN" DARK NOT GREEN DARK GREENThus, intermediate positive output voltages of 8 volts or more willchange the digital state on the output terminal 38B! and 4081 of thebrightness and greenness networks 38 and 40 and an intermdiate negativeoutput voltages of 8 volts or more will change the digital state on theoutput terminals 3882 and 4082 of said networks.

Therefore, if the quiescent (normalized state of each of the terminals383 3882, 4081, 4082 is a digital zero, the logic would appear asfollows in response to the various combinations of relative brightnessand greenness:

Digital State of Terminals Condition 3881 3882 40B! 4082. l. BRIGHT+NOTGREEN 1 O l 2. BRlGHT-i-GREEN l 0 (l l 3. DARK+NOT GREEN 0 l l 0 4.DARK+GREEN 0 l 0 l 5. BACKGROUND ONLY 0 0 0 0 Other combinations areforbidden by the high gain of the comparators 380l and 36.

Condition is used when updating the storage capacitors (4203), since noleaf T is then present over the background S.

OPERATION Referring jointly to FIGS. 1 and3, the operation of thetobacco grader 10 of the present invention will now be described. Inconsidering the following description of operation, it should berealized that the specific internal operations of the color sensingdetectors OD and RD, the detector amplifiers ODNA and RDNA, the brightor dark detector network 38, the green or yellow detector network 40 andthe background reference storage network 42 (including its components)have all been previously defined with reference to FIGS. 14, such thatpersons of ordinary skill in the art can practice the invention withregard to the two-color embodiment of FIGS. li 3.

Assuming first that no tobacco leaf T is present over the obverse faceof the background reference S, the response of the red and orange lightdetectors RD and OD is to the reflection of light from the desired colorstandard of the said reference S and can be balanced and attenuated byknown passive means in the balance network 340 such that the output ofthe brightness comparator network 380] is maintained at the same levelas the input reference voltage thereto, thereby precluding theappearance of bright or dark signals on the output terminals 388i, 3882of the bright and dark detector network 38.

The greenness set 4204 is utilized to vary the bias on the red and greendetectors RD and OD by imposing additional constraints upon the saiddetectors to vary the relative sensitivities thereof to their respectivereflected light colors, whereby the difference between the two responsescan be augmented to effectuate the desired response of the greennesscomparator network 36, the latter comprising a differential operationalamplifier for determining an orange-red difference signal. Consider, forexample, that a field effect transistor could be placed in shunt with aportion of the phototube load resistance R1 of FIG. 4, whereby theeffect of the photo-electric current through that resistance ineffecting a voltage variation at the anode ODA would clearly vary theproportionate response of the phototube OD to its selected portion ofthe spectrum, without varying the effect ofthe background referencestorage bias thereon. Furthermore. if the red and orange signals arebalanced and added in an interface, such as a conventional passive inputnetwork, at the output 32 of the voltage following detector amplifierODNA, both of these initial conditions will be compatibly imposed on thecircuit.

That is, the added signal (red orange) will indicate relative brightnessof leaf T to background reference S (normalized to a fixed referencevoltage) and the subtracted signal (orange red) will indicate relativegreenness of leafT to background reference S (normalized to a fixedreference voltage).

Upon discharge ofa leafT from the conveyor 12, the leaf T floats acrossthe obverse surface of the background reference S and if a differentcolor from the reference S, causes a change of potential on one of theoutputs 38Bl, 3BB2 of the bright and dark detector network 38,commanding the control circuit 14 to either accept or reject the leaf Ton the basis of relative brightness.

Concurrently, if the difference signal (orange-red) is of sufficientmagnitude, the logic of the output termi nals 40Bl,4(lB2 of the green oryellow detector network 40 will change, commanding the control circuit14 to either accept or reject the leaf T on the basis of relativegreenness.

Therefore, these logic signals enter the logic blocks 4401 an 4402 whichare synchronized by the clock generator .CG and change the state of thefollowing:

I. Initiate operation of the leaf presence timer 4202;

2. Disable the update reference gate 4201 and thereby maintain thereference voltages in the background reference store 4204 at the properlevels; and

3. Enter the dark-bright and green-not green date in the leaf colorlogic block 4402 of the logic network 44.

Subsequently, but substantially instantaneously, the brightness andgreenness data is screened by the color logic decoder 460i, preset forresponse by the color selector panel 4602, and the decoded logic isentered into the shift register 4801.

The data is shifted through register 4801 at a rate determined by theclock generator CG such that the path of travel of the leaf T, over andoff of the background reference S, will be sufficient to permit theleafT to be positioned with respect to the nozzle 20 of the pneumaticreject mechanism 18, such that the air blast 20A, if initiated, willproperly impinge upon the leaf T to constrain it in the rejecttrajectory TR and such that the reject pulse is required to be prsentfor a fixed amount of time to effect a rejection.

The shift register 4803 transmits the decoded data into the pneumaticsolenoid pulse generator 4802, thereby activating the solenoid driver4803 and energizing the pneumatic reject mechanism l8 for a duration oftime corresponding to the size of the leaf T.

Thus, if a leaf T is rejected based on its comparison with thebackground reference S, the air blast 20A is emitted from the nozzle 20at the proper time and for a sufficient duration to constrain therejected leaf T in the reject trajectory TR.

Therefore, in the mormal grading mode, those leaves T which are darkerand/or greener than the background reference S will be constrained inthe reject trajectory TR; and in the reverse grading mode, those leavesT which are lighter and/or less green than the background reference Swill be constrained in the reject trajectory TR.

By way of specific example of the grading functions of the grader ll),assuming the normal grading mode, a background reference S coloredgreenish-red-brown, and a requirement to reject only green suckers,which are both darker and greener than the background reference S, thecolor selector panel 4602 would be set such that the color logic decoder4601 would produce an output only in response to a DARK and GREEN logicsignal from the color logic storage 4402. As a result, no response ofthe logic decoder 460] would occur for the conditions DARK and NOTGREEN," BRIGHT and GREEN" or BRIGHT and NOT GREEN". Accordingly, allleaves except green suckers would be permitted to enter the accepttrajectory TA and be collected in the acceptable bin BA.

Should it be desired to remove brown and black leaves T as well as greensuckers, the color selector 4602 would be set to constrain the colorlogic decoder 4601 to additionally respond to the logic condition DARKand NOT GREEN" in the color logic storage block 4402, therebyconstraining all black and brown leaves T in the reject trajectory TRalong with the green suckers for collection in the reject bin BR.

In the foregoing example, an additional reject requirement for greenishyellow, greenish red and greenish orange leaves T might be desired.

Accordingly, since these are lighter than the background reference S,the color logic decoder 4601 would be set via the color selector 4602 torespond to LIGHT and GREEN logical state in the color storage block4402. Then, only LIGHT and NOT GREEN leaves T will be accepted by thegrader 10.

If the degree of greenness rejection is too great or relativelynon-responsive for the light leaves when normally grading, the greennessset 4204 can be adjusted via the control link 46M from the colorselector 4602, to vary the response differential between the red andorange detectors Rd and OD to either reduce or increase the sensitivityof the grader to the greenness parameter of the lighter leaves T.

What is claimed:

1. Grading and sorting means for comparing objects with a backgroundcolor reference having an obverse surface over which said objects aretransported, comprising:

a background color reference;

source means impinging polychromatic light on the obverse surface ofsaid background reference; conveyor means directing objects to be gradedover said obverse surface; first and second light detector meanspositioned over said obverse surface to receive light reflectedtherefrom and constrained to respond to first and second respectivelydistinct portions of the spectrum and providing first and second outputparameters representative of the respective intensity of the reflectedlight in said portions of the spectrum;

reference means establishing a reference parameter representative ofsaid color of said background reference and normalizing said detectormeans thereto; first computer means responsive to at least one of saidfirst and second output parameters, comparing same with a representationof said reference parameter and generating a first intermediate outputand a first logic signal representative of the relative brightness ofeach object traversing said obverse surface to the brightness of saidsurface; second computer means deriving a difference between said firstand second output parameters and generating a second intermediate outputand a second logic signal representative of the relative color tone ofeach said object traversing said obverse surface to a preselected colortone of said surface;

means selectively sorting objects of like grade into common paths oftravel; and

logic means, responsive to said first and second logic signals andprogrammed to respond to selected ones of said logic signalsrepresenting a given grade of each of said objects relative to saidbackground reference, generating an actuating signal for said sortingmeans upon the occurrence of a said selected one of said logic signals.2. The invention defined in claim 1, wherein said reference meanscomprises data storage means, connected in a negative feedbackconfiguration with said detector means and constrained by said first andsecond intermediate outputs in the absence of an object over saidobverse surface, to effectuate and store said reference parameter andapply same as a normalizing bias to said detector means.

3. The invention defined in claim 1, where said reference meanscomprises data storage means, connected in a negative feedbackconfiguration with said detector means, constrained by said first andsecond intermediate outputs, in the absence of an object over saidobverse surface, to effectuate and store said reference parameter andapply same as a normalizing bias to said detector means, and gate meansselectively directing said intermediate outputs into said data storagemeans,

wherein said logic means further provides, in response to said first andsecond logic signals, an object presence signal; and

wherein said gate means is interconnected with said logic means toreceive said object presence signal, the latter disabling said gatemeans to preclude the imposition of a constraint on said data storagemeans by said first and second intermediate outputs during the presenceof an object over said obverse surface.

4. The invention defined in claim 1, wherein said objects comprisetobacco leaves;

said first and second portions of the spectrum comprise the orange andred bands thereof; and

said preselected color tone of said obverse surface is a green colortone.

5. The invention defined in claim 1, wherein said objects traverse saidobverse surface and fall therefrom in a normal trajectory unlessotherwise constrained; and

wherein said sorting means comprise a pneumatic jet,

selectively actuate by said logic means to emit and impinge ajet of airupon those said objects of undesirable brightness and color tonerelative to said standard color.

6. The grading and sorting means defined in claim 1, wherein saidreference means comprises data storage means, connected in a negativefeedback configuration with said detector means and constrained by saidfirst and second intermediate outputs in the absence of an object oversaid obverse surface, to effectuate and store said reference parameterand apply same as a normalizing bias to said detector means, and colortone selection means superimposing, on said first and second detectormeans, first and second sensitivity constraints, respectively, toselectively vary the individual response of said detectors to saidrespective portions of the spectrum and thereby adjust the sensitivityof said grading and sorting means to the color tone of said objectsrelative to said standard color.

7. The invention defined in claim 1, wherein said detector means eachcomprises a photoelectric cell having an anode, a cathode and a loadresistance in series with said anode and said cathode, and voltagefollower amplifier means having an input connected with said anode andan output carrying a respective one of said output parameters;

wherein said reference means comprises gate means and timing resistancemeans in series with each said load resistance, a source of referencevoltage, and storage capacitance means connected from the commonconnection between said load resistance means and said timing resistancemeans to said source of reference voltage;

' wherein said first computer means comprises a differential operationalamplifier having a first input connected to receive at least one of saidoutput pa rameters from said voltage follower amplifier means, a secondinput terminal receiving said reference voltage and having anoperational output at which is generated a voltage comprising said firstintermediate output; and.

wherein said second computing means comprises a second differentialoperational amplifier having inputs respectively receiving said outputparameters from said voltage follower amplifier means and having anoperational output at which is generated a voltage comprising saidsecond intermediate output;

said first and second intermediate outputs being fed back through saidgate means, in the absence of an object over said obverse surface,through said timing resistances.

8. The invention defined in claim 7, wherein said grading and sortingmeans further includes color tone selection means superimposing, on saidfirst and second detector means, first and second sensitivityconstraints, respectively, to selectively vary the individual responseof said detectors to said respective portions of the spectrum andthereby adjust the sensitivity of said grading and sorting means to thecolor tone of said objects relative to said standard color;

said color tone selection means including selectively variableresistance means in series with said load resistance and said timingresistance of each said detector means, into said storage capacitancemeans to thereby charge said capacitance means to a voltagerepresentative of said standard color of said background reference andplace a normalizing voltage constraint on the said anode of each of saiddetector means;

each said gate means having a control terminal connected with said logicmeans to receive said object presence signal whereby said gate isdisabled preeluding a voltage change in said storage capacitance meansduring the presence of an object over said obverse surface.

9. The invention defined in claim 1, wherein said sorting means furtherincludes delay means precluding actuation of said reject means by saidlogic means for a selected time subsequent to the advent of traverse ofone of said objects over said obverse surface.

10. The invention defined in claim 1, wherein said reference meanscomprises data storage means, connected in a negative feedbackconfiguration with said detector means and constrained by said first andsecond intermediate outputs in the absence of an object over saidobverse surface, to effectuate and store said reference parameter andapply same as a normalizing bias to said detector means, and color toneselection means superimposing, onsaid first and second detector means,first and second sensitivity constraints, respectively, to selectivelyvary the individual response to said detectors to said respectiveportions of the spectrum and thereby adjust the sensitivity of saidgrading and sorting means to variations in the relative color tone ofsaid objects;

wherein said logic'means further provides, in response to said first andsecond logic signals, an object presence signal; and

wherein said gate means is interconnected with said logic means toreceive said o bject presence signal, the latter disabling said gatemeans to preclude the imposition of a constraint on said data storagemeans by said first and second intermediate outputs during the presenceof an object over said obverse surface.

11. The invention defined in claim 1, wherein said reference meanscomprises data storage means, connected in a negative-feedbackconfiguration with said detector means and constrained by said first andsecond intermediate outputs in the absence of an object over saidobverse surface, to effectuate and store said reference parameter andapply same as a normalizing bias to said detector means;

wherein said objects traverse :said obverse surface and fall therefromin a normal trajectory unless otherwise constrained;

wherein said sorting means comprises a pneumatic jet, selectivelyactuated by said logic means to emit and impinge a jet of air upon thosesaid objects of undesirable brightness and color tone relative to saidstandard color.

12. The invention defined in claim 1, wherein said reference meanscomprises data storage means, connected in a negative feedbackconfiguration with said detector means, constrained by said first andsecond intermediate outputs, in the absence of an object over saidobverse surface, to effectuate and store said detector means, and gatemeans selectively directing said intermediate outputs into said datastorage means;

wherein said logic means further provides, in response to said first andsecond logic signals, an object presence signal;

wherein said gate means is interconnected with said logic means toreceive said object presence signal, the latter disabling said gatemeans to preclude the imposition of a constraint on said data storagemeans by said first and second intermediate outputs during the presenceof an object over said obverse surface;

wherein said objects traverse said obverse surface and fall therefrom ina normal trajectory unless otherwise constrained; and

wherein said sorting means comprises a pneumatic jet, selectivelyactuated by said logic means to emit and impinge a jet of air upon thosesaid objects of undesirable brightness and color tone relative to saidstandard color and constrain another trajectory thereon.

13. The invention defined in claim 1, wherein said reference meanscomprises data storage means, connected in a negative feedbackconfiguration with said detector means and constrained by said first andsecond intermediate outputs in the absence of an object over saidobverse surface, to effectuate and store said reference parameter andapply same as a nonnalizing bias to said detector means, and color toneselection means superimposing, on said first and second detector means,first and second sensitivity constraints, respectively, to selectivelyvary the individual response to said detectors to said respectiveportions of the spectrum and thereby adjust the sensitivity of saidgrading and sorting means to variations in the relative color tone ofsaid objects;

wherein said objects traverse said obverse surface and fall therefrom ina normal trajectory unless otherwise constrained; and

wherein said sorting means comprises a pneumatic jet, selectivelyactuated by said logic means to emit and impinge a jet of air upon thosesaid objects of undesirable brightness and color tone relative to saidstandard color to constrain another trajectory thereon.

14. The invention defined in claim 1, wherein said objects traverse saidobverse surface and fall therefrom in a normal trajectory unlessotherwise constrained;

wherein said sorting means comprise a pneumatic jet,

' selectively actuated by said logic means to emit and impinge ajet ofair upon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon;and

wherein said sorting means further includes delay means precludingactuation of said sorting means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.

15. The invention defined in claim 1, wherein said reference meanscomprises data storage means, connected in a negative feedbackconfiguration with said detector means and constrained by said first andsecond intermediate outputs in the absence of an object over saidobverse surface, to effectuate and store said reference parameter andapply same as a normalizing bias to said detector means, and color toneselection means superimposing, on said first and second detector means,first and second sensitivity constraints, respectively, to selectivelyvary the individual response to said detectors to said respectiveportions of the spectrum and thereby adjust the sensitivity of saidgrading and sorting means to variations in the relative color tone ofsaid objects;

wherein said logic means further provides, in response to said first andsecond logic signals, an object presence signal; and wherein said gatemeans is interconnected with said logic means to receive said objectpresence signal, the latter disabling said gate means to preclude theimposition of a constraint on said data storage means by said first andsecond intermediate outputs during the presence of an object over saidobverse surface;

wherein said objects traverse said obverse surface and fall therefrom ina normal trajectory unless otherwise constrained; and

wherein said sorting means comprise a pneumatic jet,

selectively actuated by said logic means to emit and impinge ajet of airupon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon.

l6. Transducer means determining the relative brightness and greennessof tobacco leaves and the like to a known color standard comprising:

a reference surface having a standard color;

source means impinging polychromatic light on the obverse surface ofsaid reference standard to refleet light therefrom;

24 first and second detector means receiving reflected light from saidobverse surface in the red and orange bands of the spectrum,respectively, and producing first and second output parametersrepresentative of the respective intensities of said red and orangereflected light, said parameters being modified in response to the colorof a leaf present over said obverse surface;

feedback means including gated data storage means responsive to saidoutput parameters normalizing the respective output parameters of saiddetector means to said standard color;

logic means precluding further response of said storage means to saidoutput parameters in response to the presence of a leaf over saidobverse surface; and

computer means, responsive to said modified output parameters of saidfirst and second detector means, responding to at least one of saidmodified parame-' ters to derive a first signal representing therelative brightness of said leaf to said standard color, and subtractingsaid modified parameters to derive a second signal representing therelative greenness of said leaf to said standard color.

17. The invention defined in claim 16, wherein said transducer meansfurther includes control means selectively programmed to respond to saidfirst and second signals from said computer means to impose a physicalconstraint on each leaf of preselected brightness and greenness relativeto said standard color.

18. The invention defined in claim 17, wherein said control meansincludes pneumatic jet means selectively directing a jet of air againstand effecting a predetermined displacement of each said leaf ofpreselected brightness and greenness relative to said standard color.

19. The invention defined in claim 16, wherein said red and orange bandsof the spectrum are defined by broad band red and orange optical filterscentered at 655 nm and 600 nm, respectively, said red filter being sodisposed as to view said obverse surface through said orange filter.

20. The invention defined in claim 16, wherein said red and orange bandsof the spectrum are defined by broad band red and orange optical filterscentered at 655 nm and 600 nm, respectively, said red filter being sodisposed as to view said obverse surface through said orange filter;

said red filter being disposed at an angle to said obverse surface toreflect said orange band from the front surface thereof;

said first detector means disposed including first photoelectric meansto receive light through said red filter; and

said second detector means including second photoelectric means disposedto receive light reflected from the front surface of said red filter.

21. Circuit means detecting and providing an output signalrepresentative of the relative brightness of an object with reference tothe color of the obverse surface of a background reference over whichsaid object is passed, comprising, photoelectric means responsive tolight reflected from said surface in a selected band of the spectrum toproduce a color output signal representative of the intensity ofreflected light in said band;

differential operational amplifier means including first and secondinputs, an output and a source of reference potential connected with oneof said inputs, the other of said inputs being connected to receive saidoutput signal;

said amplifier means producing an operational signal,

at said output, representative of the change in said output signal froma given normalized level; and

feedback means from said output to said other of said inputs holdingsaid operational output signal at said reference voltage and normalizingsaid color output signal to said reference voltage in the absence of asaid object over said surface;

said feedback means comprising gate means and voltage storage meansselectively connected between said output and said photoelectric meansby said gate means; and

control means disabling said gate means in response to the presence of asaid object over said surface.

22. The invention defined in claim 21, wherein said voltage storagemeans comprises timing resistance means and a non-polarized capacitancemeans connected from said source of reference voltage to said gate meansthrough said timing resistance means.

23. The invention defined in claim 21, wherein said voltage storagemeans comprises timing resistance means and a non-polarized capacitancemeans connected from said source of reference voltage to said gate meansthrough said timing resistance means; and wherein said control meansincludes pulse generating means applying variable duration controlpulses to said gate means to selectively vary the rate of information tosaid voltage storage means as a function of the apparent duration of thepresence of a said object over the said surface of said backgroundreference.

24. The invention defined in claim 21, wherein said photoelectric meansincludes a phototube and a load resistance in series therewith, bothconnected in series with said gate means; and

wherein said voltage storage means comprises timing resistance means anda non-polarized capacitance means connected from said source ofreference voltage to said gate means through said timing resistancemeans;

said timing resistance being in series with said load resistance andphototube and said capacitance means being in parallel therewith.

25. The invention defined in claim 21, wherein said photoelectric meansincludes a phototube and a load resistance in series therewith, bothconnected in series with said gate means, and

wherein said voltage storage means comprises timing resistance means anda non-polarized capacitance means connected from said source ofreference voltage to said gate means through said timing resistancemeans;

said timing resistance being in series with said load resistance andphototube and said capacitance means being in parallel therewith; and

wherein said control means includes pulse generating means applyingvariable duration control pulses to said gate means to selectively varythe rate of input of information to said voltage storage means.

26. Transducer means determining the relative brightness and color toneof tobacco leaves and the like to a known color standard comprising:

a reference surface having a standard color;

source means impinging polychromatic light on the obverse surface ofsaid reference standard to reflect light therefrom;

first and second detector means receiving reflected light from saidobverse surface in first and second and of the spectrum, respectively,and producing first and second output parameters representative of therespective intensities of reflected light in said respective bands saidparameters being modified in response to the color of a leaf presentover said obverse surface; feedback means including gated data storagemeans responsive to said output parameters normalizing the respectiveoutput parameters of said detector means to said standard color;

logic means precluding further response of said storage means to saidoutput parameters in response to the presence of a leaf over saidobverse surface; and

computer means, responsive to said modified output parameters of saidfirst and second detector means, responding to at least one of saidmodified parameters to derive a first signal representing the relativebrightness of said leaf to said standard color, and subtracting saidmodified parameters to derive a second signal representing the relativecolor tone of said leaf to said standard color.

27. The invention defined in claim 26, wherein said transducer meansfurther includes control means selectively programmed to respond to saidfirst and second signals from said computer means to impose a physicalconstraint on each leaf of preselected brightness and color tonerelative to said standard color.

28. The invention defined in claim 26, wherein said control meansincludes pneumatic jet means selectively directing a jet of air againstand effecting a predetermined displacement of each said leaf ofpreselected brightness and color tone relative to said standard color.

29. Grading and sorting means for comparing objects with a backgroundcolor reference having an obverse surface over which said objects aretransported, comprising:

a background color reference;

source means impinging polychromatic light on the obverse surface ofsaid background reference; conveyor means directing objects to be gradedover said obverse surface; first and second light detector meanspositioned over said obverse surface to receive light reflectedtherefrom and constrained to respond to first and second respectivelydistinct portions of the spectrum and providing first and second outputparameters representative of the respective intensity of the reflectedlight in said portions of the spectrum;

reference means establishing a reference parameter representative ofsaid color of said background reference and normalizing said detectormeans thereto;

first computer means responsive to at least one of said first andsecond'output parameters, comparing same with a representation of saidreference parameter and generating a first logic signal representativeof the relative brightness of each object traversing said obversesurface to the brightness of said surface;

second computer means deriving a difference between said first andsecond output parameters and generating a second logic signalrepresentative of the relative color tone of each said object traversingsaid obverse surface to a preselected color tone of said surface;

means selectively sorting objects of like grade into common paths oftravel; and

logic means, responsive to said first and second logic signals andprogrammed to respond to selected ones of said logic signalsrepresenting a given grade of each of said objects relative to saidbackground reference, generating an actuating signal for said sortingmeans upon the occurrence of a said selected one of said logic signals.

30. The invention defined in claim 29, wherein said objects comprisetobacco leaves;

said first and second portions of the spectrum comprise the orange andred bands thereof; and

said preselected color tone of said obverse surface is a green colortone.

3]. The invention defined in claim 29, wherein said objects traversesaid obverse surface and fall therefrom in a normal trajectory unlessotherwise constrained; and

wherein said sorting means comprise a pneumatic jet,

selectively actuate by said logic means to emit and impinge ajet of airupon those said objects of undesirable brightness and color tonerelative to said standard color.

32. The invention defined in claim 29, wherein said sorting meansfurther includes delay means precluding actuation of said reject meansby said logic means for a selected time subsequent to the advent oftraverse of one of said objects over said obverse surface.

33. The invention defined in claim 29, wherein said objects traversesaid obverse surface and fall therefrom in a normal trajectory unlessotherwise constrained;

wherein said sorting means comprise a pneumatic jet,

selectively actuated by said logic means to emit and impinge ajet of airupon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon;and

wherein said sorting means further includes delay means precludingactuation of said sorting means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.

34. Grading and sorting means for comparing objects with a backgroundcolor reference having an obverse surface over which said objects aretransported, comprising:

a background color reference;

source means impinging polychromatic light on the obverse surface ofsaid background reference; conveyor means directing objects to be gradedover said obverse surface;

first and second light detector means positioned over said obversesurface to receive light reflected therefrom and constrained to respondto first and second respectively distinct portions of the spectrum andproviding first and second output parameters representative of therespective intensity of the reflected light in said portions of thespectrum;

reference means establishing a reference parameter representative ofsaid color of said background reference and normalizing said detectormeans thereto;

computer means responsive to at least one of said first and secondoutput parameters, comparing same with a representation of saidreference parameter and generating a first logic signal representativeof the relative brightness of each object traversing said obversesurface to the brightness of said surface and deriving a differencebetween said first and second output parameters and generating a secondlogic signal representative of the relative color tone of each saidobject traversing said obverse surface to a preselected color tone ofsaid surface;

means selectively sorting objects of like grade into common paths oftravel; and

logic means, responsive to said first and second logic signals andprogrammed to respond to selected ones of said logic signalsrepresenting a given grade of each of said objects relative to saidbackground reference, generating an actuating signal for said sortingmeans upon the occurrence of a said selected one of said logic signals.

35. The invention defined in claim 34, wherein said objects comprisetobacco leaves;

said first and second portions of the spectrum comprise the orange andred bands thereof; and

said preselected color tone of said obverse surface is a green colortone.

36. The invention defined in claim 34, wherein said objects traversesaid obverse surface and fall therefrom in a normal trajectory unlessotherwise constrained; and

wherein said sorting means comprise a pneumatic jet,

selectively actuate by said logic means to emit and impinge ajet of airupon those said objects of undesirable brightness and color tonerelative to said standard color.

37. The invention defined in claim 34, wherein said sorting meansfurther includes delay means precluding actuation of said reject meansby said logic means for a selected time subsequent to the advent oftraverse of one of said objects over said obverse surface.

38. The invention defined in claim 34, wherein said objects traversesaid obverse surface and fall therefrom in a normal trajectory unlessotherwise constrained;

wherein said sorting means comprise a pneumatic jet,

selectively actuated by said logic means to emit and impinge ajet ofairupon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon;and

wherein said sorting means further includes delay means precludingactuation of said sorting means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.

1. Grading and sorting means for comparing objects with a backgroundcolor reference having an obverse surface over which said objects aretransported, comprising: a background color reference; source meansimpinging polychromatic light on the obverse surface of said backgroundreference; conveyor means directing objects to be graded over saidobverse surface; first and second light detector means positioned oversaid obverse surface to receive light reflected therefrom andconstrained to respond to first and second respectively distinctportions of the spectrum and providing first and second outputparameters representative of the respective intensity of the reflectedlight in said portions of the spectrum; reference means establishing areference parameter representative of said color of said backgroundreference and normalizing said detector means thereto; first computermeans responsive to at least one of said first and second outputparameters, comparing same with a representation of said referenceparameter and generating a first intermediate output and a first logicsignal representative of the relative brightness of each objecttraversing said obverse surface to the brightness of said surface;second computer means deriving a difference between said first andsecond output parameters and generating a second intermediate output anda second logic signal representative of the relative color tone of eachsaid object traversing said obverse surface to a preselected color toneof said surface; means selectively sorting objects of like grade intocommon paths of travel; and logic means, responsive to said first andsecond logic signals and programmed to respond to selected ones of saidlogic signals representing a given grade of each of said objectsrelative to said background reference, generating an actuating signalfor said sorting means upon the occurrence of a said selected one ofsaid logic signals.
 2. The invention defined in claim 1, wherein saidreference means comprises data storage means, connected in a negativefeedback configuration with said detector means and constrained by saidfirst and second intermediate outputs in the absence of an object oversaid obverse surface, to effectuate and store said reference parameterand apply same as a normalizing bias to said detector means.
 3. Theinvention defined in claim 1, where said reference means comprises datastorage means, connected in a negative feedback configuraTion with saiddetector means, constrained by said first and second intermediateoutputs, in the absence of an object over said obverse surface, toeffectuate and store said reference parameter and apply same as anormalizing bias to said detector means, and gate means selectivelydirecting said intermediate outputs into said data storage means,wherein said logic means further provides, in response to said first andsecond logic signals, an object presence signal; and wherein said gatemeans is interconnected with said logic means to receive said objectpresence signal, the latter disabling said gate means to preclude theimposition of a constraint on said data storage means by said first andsecond intermediate outputs during the presence of an object over saidobverse surface.
 4. The invention defined in claim 1, wherein saidobjects comprise tobacco leaves; said first and second portions of thespectrum comprise the orange and red bands thereof; and said preselectedcolor tone of said obverse surface is a green color tone.
 5. Theinvention defined in claim 1, wherein said objects traverse said obversesurface and fall therefrom in a normal trajectory unless otherwiseconstrained; and wherein said sorting means comprise a pneumatic jet,selectively actuate by said logic means to emit and impinge a jet of airupon those said objects of undesirable brightness and color tonerelative to said standard color.
 6. The grading and sorting meansdefined in claim 1, wherein said reference means comprises data storagemeans, connected in a negative feedback configuration with said detectormeans and constrained by said first and second intermediate outputs inthe absence of an object over said obverse surface, to effectuate andstore said reference parameter and apply same as a normalizing bias tosaid detector means, and color tone selection means superimposing, onsaid first and second detector means, first and second sensitivityconstraints, respectively, to selectively vary the individual responseof said detectors to said respective portions of the spectrum andthereby adjust the sensitivity of said grading and sorting means to thecolor tone of said objects relative to said standard color.
 7. Theinvention defined in claim 1, wherein said detector means each comprisesa photoelectric cell having an anode, a cathode and a load resistance inseries with said anode and said cathode, and voltage follower amplifiermeans having an input connected with said anode and an output carrying arespective one of said output parameters; wherein said reference meanscomprises gate means and timing resistance means in series with eachsaid load resistance, a source of reference voltage, and storagecapacitance means connected from the common connection between said loadresistance means and said timing resistance means to said source ofreference voltage; wherein said first computer means comprises adifferential operational amplifier having a first input connected toreceive at least one of said output parameters from said voltagefollower amplifier means, a second input terminal receiving saidreference voltage and having an operational output at which is generateda voltage comprising said first intermediate output; and wherein saidsecond computing means comprises a second differential operationalamplifier having inputs respectively receiving said output parametersfrom said voltage follower amplifier means and having an operationaloutput at which is generated a voltage comprising said secondintermediate output; said first and second intermediate outputs beingfed back through said gate means, in the absence of an object over saidobverse surface, through said timing resistances.
 8. The inventiondefined in claim 7, wherein said grading and sorting means furtherincludes color tone selection means superimposing, on said first andsecond detector means, first and second sensitivity constraints,respectively, to selectively vary the individual response of saiddetectors to said respective portions of the spectrum and thereby adjustthe sensitivity of said grading and sorting means to the color tone ofsaid objects relative to said standard color; said color tone selectionmeans including selectively variable resistance means in series withsaid load resistance and said timing resistance of each said detectormeans, into said storage capacitance means to thereby charge saidcapacitance means to a voltage representative of said standard color ofsaid background reference and place a normalizing voltage constraint onthe said anode of each said detector means; each said gate means havinga control terminal connected with said logic means to receive saidobject presence signal whereby said gate is disabled precluding avoltage change in said storage capacitance means during the presence ofan object over said obverse surface.
 9. The invention defined in claim1, wherein said sorting means further includes delay means precludingactuation of said reject means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.
 10. The invention defined in claim 1, wherein saidreference means comprises data storage means, connected in a negativefeedback configuration with said detector means and constrained by saidfirst and second intermediate outputs in the absence of an object oversaid obverse surface, to effectuate and store said reference parameterand apply same as a normalizing bias to said detector means, and colortone selection means superimposing, on said first and second detectormeans, first and second sensitivity constraints, respectively, toselectively vary the individual response to said detectors to saidrespective portions of the spectrum and thereby adjust the sensitivityof said grading and sorting means to variations in the relative colortone of said objects; wherein said logic means further provides, inresponse to said first and second logic signals, an object presencesignal; and wherein said gate means is interconnected with said logicmeans to receive said object presence signal, the latter disabling saidgate means to preclude the imposition of a constraint on said datastorage means by said first and second intermediate outputs during thepresence of an object over said obverse surface.
 11. The inventiondefined in claim 1, wherein said reference means comprises data storagemeans, connected in a negative feedback configuration with said detectormeans and constrained by said first and second intermediate outputs inthe absence of an object over said obverse surface, to effectuate andstore said reference parameter and apply same as a normalizing bias tosaid detector means; wherein said objects traverse said obverse surfaceand fall therefrom in a normal trajectory unless otherwise constrained;wherein said sorting means comprises a pneumatic jet, selectivelyactuated by said logic means to emit and impinge a jet of air upon thosesaid objects of undesirable brightness and color tone relative to saidstandard color.
 12. The invention defined in claim 1, wherein saidreference means comprises data storage means, connected in a negativefeedback configuration with said detector means, constrained by saidfirst and second intermediate outputs, in the absence of an object oversaid obverse surface, to effectuate and store said detector means, andgate means selectively directing said intermediate outputs into saiddata storage means; wherein said logic means further provides, inresponse to said first and second logic signals, an object presencesignal; wherein said gate means is interconnected with said logic meansto receive said object presence signal, the latter disabling said gatemeans to preclude the imposition of a constraint on said data storagemeans by said first and second intermediate outputs during the presenceof an object over said obverse surface; wherein said objects traversesaid obverse surface and fall therefrom in a normal trajectory unlessotherwise constrained; and wherein said sorting means comprises apneumatic jet, selectively actuated by said logic means to emit andimpinge a jet of air upon those said objects of undesirable brightnessand color tone relative to said standard color and constrain anothertrajectory thereon.
 13. The invention defined in claim 1, wherein saidreference means comprises data storage means, connected in a negativefeedback configuration with said detector means and constrained by saidfirst and second intermediate outputs in the absence of an object oversaid obverse surface, to effectuate and store said reference parameterand apply same as a normalizing bias to said detector means, and colortone selection means superimposing, on said first and second detectormeans, first and second sensitivity constraints, respectively, toselectively vary the individual response to said detectors to saidrespective portions of the spectrum and thereby adjust the sensitivityof said grading and sorting means to variations in the relative colortone of said objects; wherein said objects traverse said obverse surfaceand fall therefrom in a normal trajectory unless otherwise constrained;and wherein said sorting means comprises a pneumatic jet, selectivelyactuated by said logic means to emit and impinge a jet of air upon thosesaid objects of undesirable brightness and color tone relative to saidstandard color to constrain another trajectory thereon.
 14. Theinvention defined in claim 1, wherein said objects traverse said obversesurface and fall therefrom in a normal trajectory unless otherwiseconstrained; wherein said sorting means comprise a pneumatic jet,selectively actuated by said logic means to emit and impinge a jet ofair upon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon;and wherein said sorting means further includes delay means precludingactuation of said sorting means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.
 15. The invention defined in claim 1, wherein saidreference means comprises data storage means, connected in a negativefeedback configuration with said detector means and constrained by saidfirst and second intermediate outputs in the absence of an object oversaid obverse surface, to effectuate and store said reference parameterand apply same as a normalizing bias to said detector means, and colortone selection means superimposing, on said first and second detectormeans, first and second sensitivity constraints, respectively, toselectively vary the individual response to said detectors to saidrespective portions of the spectrum and thereby adjust the sensitivityof said grading and sorting means to variations in the relative colortone of said objects; wherein said logic means further provides, inresponse to said first and second logic signals, an object presencesignal; and wherein said gate means is interconnected with said logicmeans to receive said object presence signal, the latter disabling saidgate means to preclude the imposition of a constraint on said datastorage means by said first and second intermediate outputs during thepresence of an object over said obverse surface; wherein said objectstraverse said obverse surface and fall therefrom in a normal trajectoryunless otherwise constrained; and wherein said sorting means comprise apneumatic jet, selectively actuated by said logic means to emit andimpinge a jet of air upon those said objects of undesirable brightnessand color tone relative to said standard color to constrain anothertrajectory thereon.
 16. Transducer means determining the relativebrightness and greenness of tobacco leaves and the like to a known colorstandard comprising: a reference surface having A standard color; sourcemeans impinging polychromatic light on the obverse surface of saidreference standard to reflect light therefrom; first and second detectormeans receiving reflected light from said obverse surface in the red andorange bands of the spectrum, respectively, and producing first andsecond output parameters representative of the respective intensities ofsaid red and orange reflected light, said parameters being modified inresponse to the color of a leaf present over said obverse surface;feedback means including gated data storage means responsive to saidoutput parameters normalizing the respective output parameters of saiddetector means to said standard color; logic means precluding furtherresponse of said storage means to said output parameters in response tothe presence of a leaf over said obverse surface; and computer means,responsive to said modified output parameters of said first and seconddetector means, responding to at least one of said modified parametersto derive a first signal representing the relative brightness of saidleaf to said standard color, and subtracting said modified parameters toderive a second signal representing the relative greenness of said leafto said standard color.
 17. The invention defined in claim 16, whereinsaid transducer means further includes control means selectivelyprogrammed to respond to said first and second signals from saidcomputer means to impose a physical constraint on each leaf ofpreselected brightness and greenness relative to said standard color.18. The invention defined in claim 17, wherein said control meansincludes pneumatic jet means selectively directing a jet of air againstand effecting a predetermined displacement of each said leaf ofpreselected brightness and greenness relative to said standard color.19. The invention defined in claim 16, wherein said red and orange bandsof the spectrum are defined by broad band red and orange optical filterscentered at 655 nm and 600 nm, respectively, said red filter being sodisposed as to view said obverse surface through said orange filter. 20.The invention defined in claim 16, wherein said red and orange bands ofthe spectrum are defined by broad band red and orange optical filterscentered at 655 nm and 600 nm, respectively, said red filter being sodisposed as to view said obverse surface through said orange filter;said red filter being disposed at an angle to said obverse surface toreflect said orange band from the front surface thereof; said firstdetector means disposed including first photoelectric means to receivelight through said red filter; and said second detector means includingsecond photoelectric means disposed to receive light reflected from thefront surface of said red filter.
 21. Circuit means detecting andproviding an output signal representative of the relative brightness ofan object with reference to the color of the obverse surface of abackground reference over which said object is passed, comprising,photoelectric means responsive to light reflected from said surface in aselected band of the spectrum to produce a color output signalrepresentative of the intensity of reflected light in said band;differential operational amplifier means including first and secondinputs, an output and a source of reference potential connected with oneof said inputs, the other of said inputs being connected to receive saidoutput signal; said amplifier means producing an operational signal, atsaid output, representative of the change in said output signal from agiven normalized level; and feedback means from said output to saidother of said inputs holding said operational output signal at saidreference voltage and normalizing said color output signal to saidreference voltage in the absence of a said object over said surface;said feedback means comprising gate means and voltage storage meansselectively connected betwEen said output and said photoelectric meansby said gate means; and control means disabling said gate means inresponse to the presence of a said object over said surface.
 22. Theinvention defined in claim 21, wherein said voltage storage meanscomprises timing resistance means and a non-polarized capacitance meansconnected from said source of reference voltage to said gate meansthrough said timing resistance means.
 23. The invention defined in claim21, wherein said voltage storage means comprises timing resistance meansand a non-polarized capacitance means connected from said source ofreference voltage to said gate means through said timing resistancemeans; and wherein said control means includes pulse generating meansapplying variable duration control pulses to said gate means toselectively vary the rate of information to said voltage storage meansas a function of the apparent duration of the presence of a said objectover the said surface of said background reference.
 24. The inventiondefined in claim 21, wherein said photoelectric means includes aphototube and a load resistance in series therewith, both connected inseries with said gate means; and wherein said voltage storage meanscomprises timing resistance means and a non-polarized capacitance meansconnected from said source of reference voltage to said gate meansthrough said timing resistance means; said timing resistance being inseries with said load resistance and phototube and said capacitancemeans being in parallel therewith.
 25. The invention defined in claim21, wherein said photoelectric means includes a phototube and a loadresistance in series therewith, both connected in series with said gatemeans, and wherein said voltage storage means comprises timingresistance means and a non-polarized capacitance means connected fromsaid source of reference voltage to said gate means through said timingresistance means; said timing resistance being in series with said loadresistance and phototube and said capacitance means being in paralleltherewith; and wherein said control means includes pulse generatingmeans applying variable duration control pulses to said gate means toselectively vary the rate of input of information to said voltagestorage means.
 26. Transducer means determining the relative brightnessand color tone of tobacco leaves and the like to a known color standardcomprising: a reference surface having a standard color; source meansimpinging polychromatic light on the obverse surface of said referencestandard to reflect light therefrom; first and second detector meansreceiving reflected light from said obverse surface in first and secondand of the spectrum, respectively, and producing first and second outputparameters representative of the respective intensities of reflectedlight in said respective bands said parameters being modified inresponse to the color of a leaf present over said obverse surface;feedback means including gated data storage means responsive to saidoutput parameters normalizing the respective output parameters of saiddetector means to said standard color; logic means precluding furtherresponse of said storage means to said output parameters in response tothe presence of a leaf over said obverse surface; and computer means,responsive to said modified output parameters of said first and seconddetector means, responding to at least one of said modified parametersto derive a first signal representing the relative brightness of saidleaf to said standard color, and subtracting said modified parameters toderive a second signal representing the relative color tone of said leafto said standard color.
 27. The invention defined in claim 26, whereinsaid transducer means further includes control means selectivelyprogrammed to respond to said first and second signals from saidcomputer means to impose a physical constraint on each leaf ofpreselected brightness and color tone relative to said standard color.28. The invention defined in claim 26, wherein said control meansincludes pneumatic jet means selectively directing a jet of air againstand effecting a predetermined displacement of each said leaf ofpreselected brightness and color tone relative to said standard color.29. Grading and sorting means for comparing objects with a backgroundcolor reference having an obverse surface over which said objects aretransported, comprising: a background color reference; source meansimpinging polychromatic light on the obverse surface of said backgroundreference; conveyor means directing objects to be graded over saidobverse surface; first and second light detector means positioned oversaid obverse surface to receive light reflected therefrom andconstrained to respond to first and second respectively distinctportions of the spectrum and providing first and second outputparameters representative of the respective intensity of the reflectedlight in said portions of the spectrum; reference means establishing areference parameter representative of said color of said backgroundreference and normalizing said detector means thereto; first computermeans responsive to at least one of said first and second outputparameters, comparing same with a representation of said referenceparameter and generating a first logic signal representative of therelative brightness of each object traversing said obverse surface tothe brightness of said surface; second computer means deriving adifference between said first and second output parameters andgenerating a second logic signal representative of the relative colortone of each said object traversing said obverse surface to apreselected color tone of said surface; means selectively sortingobjects of like grade into common paths of travel; and logic means,responsive to said first and second logic signals and programmed torespond to selected ones of said logic signals representing a givengrade of each of said objects relative to said background reference,generating an actuating signal for said sorting means upon theoccurrence of a said selected one of said logic signals.
 30. Theinvention defined in claim 29, wherein said objects comprise tobaccoleaves; said first and second portions of the spectrum comprise theorange and red bands thereof; and said preselected color tone of saidobverse surface is a green color tone.
 31. The invention defined inclaim 29, wherein said objects traverse said obverse surface and falltherefrom in a normal trajectory unless otherwise constrained; andwherein said sorting means comprise a pneumatic jet, selectively actuateby said logic means to emit and impinge a jet of air upon those saidobjects of undesirable brightness and color tone relative to saidstandard color.
 32. The invention defined in claim 29, wherein saidsorting means further includes delay means precluding actuation of saidreject means by said logic means for a selected time subsequent to theadvent of traverse of one of said objects over said obverse surface. 33.The invention defined in claim 29, wherein said objects traverse saidobverse surface and fall therefrom in a normal trajectory unlessotherwise constrained; wherein said sorting means comprise a pneumaticjet, selectively actuated by said logic means to emit and impinge a jetof air upon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon;and wherein said sorting means further includes delay means precludingactuation of said sorting means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.
 34. Grading and sorting means for comparing objectswith a background color reference having an obverse surface over whichsaid objects are transported, comprising: a background color reference;SOURCE means impinging polychromatic light on the obverse surface ofsaid background reference; conveyor means directing objects to be gradedover said obverse surface; first and second light detector meanspositioned over said obverse surface to receive light reflectedtherefrom and constrained to respond to first and second respectivelydistinct portions of the spectrum and providing first and second outputparameters representative of the respective intensity of the reflectedlight in said portions of the spectrum; reference means establishing areference parameter representative of said color of said backgroundreference and normalizing said detector means thereto; computer meansresponsive to at least one of said first and second output parameters,comparing same with a representation of said reference parameter andgenerating a first logic signal representative of the relativebrightness of each object traversing said obverse surface to thebrightness of said surface and deriving a difference between said firstand second output parameters and generating a second logic signalrepresentative of the relative color tone of each said object traversingsaid obverse surface to a preselected color tone of said surface; meansselectively sorting objects of like grade into common paths of travel;and logic means, responsive to said first and second logic signals andprogrammed to respond to selected ones of said logic signalsrepresenting a given grade of each of said objects relative to saidbackground reference, generating an actuating signal for said sortingmeans upon the occurrence of a said selected one of said logic signals.35. The invention defined in claim 34, wherein said objects comprisetobacco leaves; said first and second portions of the spectrum comprisethe orange and red bands thereof; and said preselected color tone ofsaid obverse surface is a green color tone.
 36. The invention defined inclaim 34, wherein said objects traverse said obverse surface and falltherefrom in a normal trajectory unless otherwise constrained; andwherein said sorting means comprise a pneumatic jet, selectively actuateby said logic means to emit and impinge a jet of air upon those saidobjects of undesirable brightness and color tone relative to saidstandard color.
 37. The invention defined in claim 34, wherein saidsorting means further includes delay means precluding actuation of saidreject means by said logic means for a selected time subsequent to theadvent of traverse of one of said objects over said obverse surface. 38.The invention defined in claim 34, wherein said objects traverse saidobverse surface and fall therefrom in a normal trajectory unlessotherwise constrained; wherein said sorting means comprise a pneumaticjet, selectively actuated by said logic means to emit and impinge a jetof air upon those said objects of undesirable brightness and color tonerelative to said standard color to constrain another trajectory thereon;and wherein said sorting means further includes delay means precludingactuation of said sorting means by said logic means for a selected timesubsequent to the advent of traverse of one of said objects over saidobverse surface.